A scientist extracts an enzyme from potato cells. The enzyme joins glucose molecules to make starch, and its optimum pH is 8.
The scientist adds the enzyme to a glucose solution buffered at pH 2.
What happens to the rate at which starch is made, compared with the rate at pH 8?
It increases because the acidic conditions make glucose molecules collide with the enzyme more often.
It decreases because the extreme pH denatures the enzyme, so glucose molecules cannot bind.
It stays the same because an enzyme remains unchanged when it catalyses a reaction.
It decreases because glucose molecules denature and can no longer be joined into starch.
184 exam-style questions on OCR GCSE Biology 1.2 What happens in cells (and what do cells need)?, covering 1.2.1 Structure of DNA, 1.2.2 Nucleotides and complementary bases, 1.2.3 Protein synthesis, 1.2.4 DNA structure and the proteins made, 1.2.5 Investigating enzymatic reactions, and 1.2.6 Mechanism of enzyme action. Each one has a worked solution and a mark scheme showing where the marks go.